From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1B6BC433EF for ; Thu, 17 Feb 2022 08:20:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237468AbiBQIUa (ORCPT ); Thu, 17 Feb 2022 03:20:30 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:36236 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237434AbiBQIUZ (ORCPT ); Thu, 17 Feb 2022 03:20:25 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 13D0D297226 for ; Thu, 17 Feb 2022 00:20:11 -0800 (PST) Received: from dggeme756-chm.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4JznlV5lmXz9sm2; Thu, 17 Feb 2022 16:18:30 +0800 (CST) Received: from [10.67.110.136] (10.67.110.136) by dggeme756-chm.china.huawei.com (10.3.19.102) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.21; Thu, 17 Feb 2022 16:20:08 +0800 Subject: Re: [PATCH -v2] powerpc/process, kasan: Silence KASAN warnings in __get_wchan() To: , , , , , , , , CC: , , , References: <20220119015025.136902-1-heying24@huawei.com> <20220121014418.155675-1-heying24@huawei.com> From: He Ying Message-ID: <06c5f730-c383-34f9-778f-6845ca36c718@huawei.com> Date: Thu, 17 Feb 2022 16:20:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20220121014418.155675-1-heying24@huawei.com> Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.110.136] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggeme756-chm.china.huawei.com (10.3.19.102) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Michael, Kindly ping. This patch may be missed. Would you please pick it? Or does it need more review? ÔÚ 2022/1/21 9:44, He Ying дµÀ: > The following KASAN warning was reported in our kernel. > > BUG: KASAN: stack-out-of-bounds in get_wchan+0x188/0x250 > Read of size 4 at addr d216f958 by task ps/14437 > > CPU: 3 PID: 14437 Comm: ps Tainted: G O 5.10.0 #1 > Call Trace: > [daa63858] [c0654348] dump_stack+0x9c/0xe4 (unreliable) > [daa63888] [c035cf0c] print_address_description.constprop.3+0x8c/0x570 > [daa63908] [c035d6bc] kasan_report+0x1ac/0x218 > [daa63948] [c00496e8] get_wchan+0x188/0x250 > [daa63978] [c0461ec8] do_task_stat+0xce8/0xe60 > [daa63b98] [c0455ac8] proc_single_show+0x98/0x170 > [daa63bc8] [c03cab8c] seq_read_iter+0x1ec/0x900 > [daa63c38] [c03cb47c] seq_read+0x1dc/0x290 > [daa63d68] [c037fc94] vfs_read+0x164/0x510 > [daa63ea8] [c03808e4] ksys_read+0x144/0x1d0 > [daa63f38] [c005b1dc] ret_from_syscall+0x0/0x38 > --- interrupt: c00 at 0x8fa8f4 > LR = 0x8fa8cc > > The buggy address belongs to the page: > page:98ebcdd2 refcount:0 mapcount:0 mapping:00000000 index:0x2 pfn:0x1216f > flags: 0x0() > raw: 00000000 00000000 01010122 00000000 00000002 00000000 ffffffff 00000000 > raw: 00000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > d216f800: 00 00 00 00 00 f1 f1 f1 f1 00 00 00 00 00 00 00 > d216f880: f2 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > >d216f900: 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 > ^ > d216f980: f2 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 > d216fa00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > After looking into this issue, I find the buggy address belongs > to the task stack region. It seems KASAN has something wrong. > I look into the code of __get_wchan in x86 architecture and > find the same issue has been resolved by the commit > f7d27c35ddff ("x86/mm, kasan: Silence KASAN warnings in get_wchan()"). > The solution could be applied to powerpc architecture too. > > As Andrey Ryabinin said, get_wchan() is racy by design, it may > access volatile stack of running task, thus it may access > redzone in a stack frame and cause KASAN to warn about this. > > Use READ_ONCE_NOCHECK() to silence these warnings. > > Reported-by: Wanming Hu > Signed-off-by: He Ying > Signed-off-by: Chen Jingwen > Reviewed-by: Kees Cook > --- > Changelog: > > v2: > * Add missing Reported-by and SoB tags > --- > arch/powerpc/kernel/process.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c > index 984813a4d5dc..a75d20f23dac 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -2160,12 +2160,12 @@ static unsigned long ___get_wchan(struct task_struct *p) > return 0; > > do { > - sp = *(unsigned long *)sp; > + sp = READ_ONCE_NOCHECK(*(unsigned long *)sp); > if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD) || > task_is_running(p)) > return 0; > if (count > 0) { > - ip = ((unsigned long *)sp)[STACK_FRAME_LR_SAVE]; > + ip = READ_ONCE_NOCHECK(((unsigned long *)sp)[STACK_FRAME_LR_SAVE]); > if (!in_sched_functions(ip)) > return ip; > } From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E6F27C433EF for ; Thu, 17 Feb 2022 08:20:54 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4JznpD6SyDz3cYm for ; Thu, 17 Feb 2022 19:20:52 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=huawei.com (client-ip=45.249.212.188; helo=szxga02-in.huawei.com; envelope-from=heying24@huawei.com; receiver=) Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4Jznnj3zPWz30NP for ; Thu, 17 Feb 2022 19:20:18 +1100 (AEDT) Received: from dggeme756-chm.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4JznlV5lmXz9sm2; Thu, 17 Feb 2022 16:18:30 +0800 (CST) Received: from [10.67.110.136] (10.67.110.136) by dggeme756-chm.china.huawei.com (10.3.19.102) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.21; Thu, 17 Feb 2022 16:20:08 +0800 Subject: Re: [PATCH -v2] powerpc/process, kasan: Silence KASAN warnings in __get_wchan() To: , , , , , , , , References: <20220119015025.136902-1-heying24@huawei.com> <20220121014418.155675-1-heying24@huawei.com> From: He Ying Message-ID: <06c5f730-c383-34f9-778f-6845ca36c718@huawei.com> Date: Thu, 17 Feb 2022 16:20:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20220121014418.155675-1-heying24@huawei.com> Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.110.136] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggeme756-chm.china.huawei.com (10.3.19.102) X-CFilter-Loop: Reflected X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: chenjingwen6@huawei.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, huwanming@huaweil.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Michael, Kindly ping. This patch may be missed. Would you please pick it? Or does it need more review? ÔÚ 2022/1/21 9:44, He Ying дµÀ: > The following KASAN warning was reported in our kernel. > > BUG: KASAN: stack-out-of-bounds in get_wchan+0x188/0x250 > Read of size 4 at addr d216f958 by task ps/14437 > > CPU: 3 PID: 14437 Comm: ps Tainted: G O 5.10.0 #1 > Call Trace: > [daa63858] [c0654348] dump_stack+0x9c/0xe4 (unreliable) > [daa63888] [c035cf0c] print_address_description.constprop.3+0x8c/0x570 > [daa63908] [c035d6bc] kasan_report+0x1ac/0x218 > [daa63948] [c00496e8] get_wchan+0x188/0x250 > [daa63978] [c0461ec8] do_task_stat+0xce8/0xe60 > [daa63b98] [c0455ac8] proc_single_show+0x98/0x170 > [daa63bc8] [c03cab8c] seq_read_iter+0x1ec/0x900 > [daa63c38] [c03cb47c] seq_read+0x1dc/0x290 > [daa63d68] [c037fc94] vfs_read+0x164/0x510 > [daa63ea8] [c03808e4] ksys_read+0x144/0x1d0 > [daa63f38] [c005b1dc] ret_from_syscall+0x0/0x38 > --- interrupt: c00 at 0x8fa8f4 > LR = 0x8fa8cc > > The buggy address belongs to the page: > page:98ebcdd2 refcount:0 mapcount:0 mapping:00000000 index:0x2 pfn:0x1216f > flags: 0x0() > raw: 00000000 00000000 01010122 00000000 00000002 00000000 ffffffff 00000000 > raw: 00000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > d216f800: 00 00 00 00 00 f1 f1 f1 f1 00 00 00 00 00 00 00 > d216f880: f2 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > >d216f900: 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 > ^ > d216f980: f2 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 > d216fa00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > After looking into this issue, I find the buggy address belongs > to the task stack region. It seems KASAN has something wrong. > I look into the code of __get_wchan in x86 architecture and > find the same issue has been resolved by the commit > f7d27c35ddff ("x86/mm, kasan: Silence KASAN warnings in get_wchan()"). > The solution could be applied to powerpc architecture too. > > As Andrey Ryabinin said, get_wchan() is racy by design, it may > access volatile stack of running task, thus it may access > redzone in a stack frame and cause KASAN to warn about this. > > Use READ_ONCE_NOCHECK() to silence these warnings. > > Reported-by: Wanming Hu > Signed-off-by: He Ying > Signed-off-by: Chen Jingwen > Reviewed-by: Kees Cook > --- > Changelog: > > v2: > * Add missing Reported-by and SoB tags > --- > arch/powerpc/kernel/process.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c > index 984813a4d5dc..a75d20f23dac 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -2160,12 +2160,12 @@ static unsigned long ___get_wchan(struct task_struct *p) > return 0; > > do { > - sp = *(unsigned long *)sp; > + sp = READ_ONCE_NOCHECK(*(unsigned long *)sp); > if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD) || > task_is_running(p)) > return 0; > if (count > 0) { > - ip = ((unsigned long *)sp)[STACK_FRAME_LR_SAVE]; > + ip = READ_ONCE_NOCHECK(((unsigned long *)sp)[STACK_FRAME_LR_SAVE]); > if (!in_sched_functions(ip)) > return ip; > }